PSZCZELNICZE ZESZYTY NAUKOWERok XLIV, Nr 2 2000

LIGHT-BODIED FEMALES AS A PARAMETER USEFULIN THE ASSESSMENT OF THE INFESTATION OF BEE

COLONIES BY THE MITE VARROA JACOBSONI

Malgorzata Bienkowska, Zofia KODopacka

Research Institute of Pomology and Floriculture Apiculture Division,24-100 Pulawy, ul. Kazimierska 2

Summary

In the natural fall of dead mites along with dark females which die natural death andfall to the hive bottom as well as males and developmental stages of the mite removed bybees during cell cleaning there are also light non-coloured females. They come out of thecells together with emerging insects but are incapable of survival. The death rate of theparasite and the proportion of light and dark-coloured females in the total number of deadmites are closely related to brood emergence and to the kind of emerging brood.

The proportion of light-coloured females in the natural fall of dead mites varies andmay reach 49%, 70% and even as much as 97% as reported by Rademacher. In the studiesperformed in the Apiculture Division in the years 1988, 1990, 1992, 1995 and 1998 thepercentage of light-coloured females in the natural fall averaged 32.5% (from 25% to40.5%).

The amount of the natural fall of light-coloured females varied from year to year butthe magnitude of that fall over the years- especially in the second part of the season fromthe beginning of July to mid-September - matched the year-to-year variation in infestationlevel expressed with the total number of dark and light-coloured females after chemicalcontrol treatments. Higly significant correlations were also found between the number ofnaturally dead light-coloured females and the number of dead dark and light-colouredfemales following chemical treatments (1988 = 0.652**; 1990 = 0.768**; 1992 = 0.893**;1995 = 0.718**; 1998 = 0.899**). Each year of study is characterized by a different,peculiar rate of mite build up. The calculated differences between the autumn colonyinfestation thus estimated (expressed as the average predicted number of mites in colonies)and the actual mite fall after chemical treatments were characterized by substantialvariation from - 362 to + 826 mites. Diurnal natural fall of light-bodied females calculatedfrom shorter periods of counts cannot be treated as a reliable parameter to estimate theautumn infestation of bee colonies by the mite.

Keywords: Varroajacobsoni, light female.

INTRODUCTIONAccording to Lie big and S c h l up f (1983) the natural summer fall of

Varroa jacobsoni allows a simple and a reasonably accurate prediction of therate of infestation of bee colonies by the mite. However, based on her own

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research Ra d e m a c her (1985) concluded that the natural mite mortalitydoes not allow to predict the autumn colony infestation.

Alongside with dark-bodied females which die a natural death and fall tothe bottom of the hive, males and developmental stages of the mite removedby the bees during cell cleaning the natural mite fall also containslight-bodied, non-coloured females which come out of the cells together withemerging adult insects but which do not survive (L e Con t e and A r n old1983; S t e i n e r 1983). The magnitude of mite fall and the proportion ofdark- and light-bodied females in the fall are closely related to brood emergingand to the kind of emerging brood. The proportion of light-bodied females inthe mite fall varies and may reach 49, 70% (L i e big 1984) or even as high as97% as reported by Ra d e m a c her (1985).

The objective of the study was to explain whether the number oflight-bodied females in the natural summer mite fall can be a useful parameterin the estimation (still before the last honey harvest) of the magnitude of beecolony infestation by the mite.

MATERIAL AND METHODSThe study was conducted in the years 1988, 1990, 1992, 1995 and 1998 in

a stationary apiary of the Apiculture Division which comprised a total of 123bee colonies of the Caucassian and Carniolan bees with naturally andartificially inseminated queens placed in Dadant hives. Each year newcolonies in the same apiary were taken for observations.

Table 1Schedule of counting the natural fall of V.jacobsoni females and formulasused for control treatments - Harmonogram obserwacji naturalnego osypu

samic V.jacobsoni oraz preparaty uzyte do zabieg6w chemicznych

Number of Start to check for natural Finish to check for Varroa - killing agent applied

Year colonies fall- Termin rozp~ia natural fall (a.i.)

Rok Uczba kontroli osypu Termln zakor\czenia Zastosowany ~rOOek

rOOzin naturalnego kontrollosypu warroabOjczynaturalnego (s.a.)

1988 22 3.05 22.09 5 x Apiwarol A + Mitac (amitraz)

1990 21 3.07 13.09 4 x Apiwarol AS (amitraz)2 x Perilin (coumaphos)

1992 24 3.05 29.09 Ruwarol (fluvalinate)2 x Perilin (coumaphos)

1995 26 3.05 14.09 Apifos (bromfenvinphos)4 x Apiwarol AS (amitraz)

1998 30 3.05 15.09 Apifos (bromfenvinphos)

186

The number of Varroa jacobsoni females in the natural mite fall waschecked at one-week intervals. To this end wire net bottom inserts were usedwhich prevented the bees from getting the mites outside the hive. At the end ofthe season, in order to measure the magnitude of colony infestationVarroa-kiling agents available in a given year were used and weekly countswere also made of dead V.jacobsoni females (Table 1).

In order to characterise the dynamics of the natural fall the mobile meanmethod was used to cover three-week periods and mite counts were convertedto the diurnal fall. The method allowed to eliminate random variation of thevalues of diurnal natural fall of light-bodied V.jacobsoni females.

RESUL TS AND DISCUSSIONThe mean number of dead light-bodied females which fell to the wire net

bottom inserts stayed at a similar level in May and in June over all years of thestudy. In July and in August the number of light females rose two- to sixfoldcompared to previous month's figures which, according to research byMartin and Kemp (1997), Loob and Martin (1997), was broughtabout by intensive rearing of brood in that period (Table 2).

Table 2Changes in mortality rate of light- bodied V.jacobsoni females in consecutive

months - Zmiany smiertelnosci samic jasnych Varroa jacobsoni wnastepujacych po sobie miesiacach

Natural fall of light- bodied females (mean I colony) indiv.Year Osyp naturalny samic jasnych (~rednio I rodzin~) szt.Rok

May- Maj June - Czerwlec July - Lipiec August - Sierpie"

1988 6,81 1,73 15,1 90,8

1990 - - 40,90 143,0

1992 2,04 3,25 14,46 21,88

1995 13,04 11,81 20,73 44,19

1998 0,83 0,60 a,IT 2,46

Likewise, there was an increase in the number of V.jacobsoni females inthe diurnal natural fall calculated from counts made in three-week periods(Fig. 1). It was also found that the range between the minimum and themaximum counts of dead light females increased as the season progressedwhich was indicative not only of different colony infestation rates but also ofan uneven build-up of the mite in bee colonies.

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The percentage levels of dark- and light-bodied females in the natural fallshow that light bodied females are consistently less numerous. The lightbodies females in the fall accounted for 25% to 40.5% of the mite fall. In themite fall resulting from chemical treatments the percentage of light femaleswas very low which is obvious as the treatments were done late in the season.7,00,----------------------------

),00+-----------------------::oi~-~---

5,00+---------------------1'--------

4,00+-------------------+- ~----'~--

3,00+------------------+-----,f----~~-

2,00+-------------------:;;~-____;~-__.'_.-.:... "0";----

1,00+----------------=--'~."c----------

1988 1990 1992 1995 1998

Fig. 1 Dynamics of natural fall of V.jacobsoni females calculated from 3- week countperiod.Dynamika osypu samic jasnych V.jacobsoni na podstawie sredniej ruchomej z3-tygodniowych okres6w obserwacji.

Despite a high variation among colonies for the magnitude of infestationby the mite within a year as assessed by the total number of light and darkfemales after chemical treatments statistical analysis showed the significanceof differences between years with very high (1990), high (1988), medium-high(1995 and 1992) and low (1998) levels of Varroa incidence (Tab. 3). For thenatural fall of light females year-to year statistically significant differenceswere found only in the second part of the season from July to September.

The analysis of the natural fall of light females allows to arrange the yearsin the same order (1990, 1988, 1995, 1992 and 1998) as they ranked accordingto the magnitude of infestation (Fig. 2). It indicates a relationship between thetwo traits. Such a conclusion is warranted by highly significant correlationcoefficients between the natural summer fall of light females across the wholestudy period and in the L1 to W2 period and the total fall of dark and lightfemales following chemical treatments (Table 4).

188

Table 3Infestation of bee colonies based on the natural fall of mites and on the number

of mites dead after chemical treatment - Porazenie rodzin pszczelich przezVarroa Jacobson; na podstawie naturalnego osypu samic pasozyta i osypu po

zabiegach chemicznych

Natural mite fall during Total mite fall of dark Total mite fall of light andOsyp naturalny ~rednie (zakres) - szt. female after chemical dark females after chemical

Year treatmens average treatmens average (range)

Rok n from from total survey (range) - Osyp po Osyp po zabiegachMl - JI4 Jll - 52 period zabiegach chemicznych chemicznych samic

od od z cafego okresu samic ciemnych ~rednie ciemnych i jasnych /liClnieMl- C4 C4 - 52 obserwacji (zakres) - szt. ~rednie (zakres) szt.

1988 22 17,71 183,91b 198," 1142,4c 1150,4 c(26 - 583) (266 - 2461) (266 - 2463)

1990 21 - 227,1 b 227,1· 1m,Od 1848,11d(43 - 648) (510 - 3220) (510 - 3350)

1992 24 13,3 a 48,91 54,61 650,5 b 652,7b(91 - 241) (104 - 2276) (104 - 2288)

1995 26 36,7 a 93,511a 118,41 165,3 be .,7be(0 - 705) (125 - 2714) (146 - 2986)

1998 30 2,2 a 6,41 7," 140,81 145,81(0 - 57) (2 - 883) (2 - 953)

• - data not taken into consideration in the statistical analysis

2~.------------=~------------------~-------------------Iii Total mite fall after chemical treatrnensdig Liczba samic po zabiegach chemicznych

I Natural mite fall during total survey periodNaturalny osyp samic jasnych w czasie caIego okresu obserwacji

D Natural mite fall from JI 1 to 52Naturalny osyp samic jasnych od L 1 do W2

2000 +-=::------

500

1500

1000

o1990 1988 1995 1992 1998

Fig. 2 Mean number of all female mites following chemical treatments and naturalfall of light coloured mitesSrednia liczba wszystkich samic pasozyta martwych po zabiegachchemicznych i osyp naturalny samic jasnych

\

189

~--- .. _--- ._- ._--------

Table 4Values of regression, correlation and determination coefficients for the natural

fall of Varroa jacobsont light-bodied females (x) vs. the fall light anddark-bodied females following chemical control (y). - Wartosci

wsp61czynnik6wregresji, korelacji i determinacji dla osypu naturalnego samicjasnych V.jacobsoni (x) wzgledem osypu samic ciemnych i jasnych po

zabiegach chemicznych (y)

Total surrey perlod Period from JI1 to S2Year Caly okres obserwacji Okres od C1 do W2Rok

b a rxy 0 b a rxy 0

1990 - - - - 3,23 1113,8 0,768** 59%

1988 2,11 735,n 0,652** 43% 2,02 819,04 0,550* 30%

1995 3,69 537,09 0,718** 52% 4,03 578,09 0,704** 50%

1992 8,17 206,68 0,894** 80% 9,12 206,86 0,940** 88%

1998 17,01 11,79 0,889** 79% 19,84 18,03 0,902** 81%

b-regression coeff.; a-free term; r-correlation coeff.; D-determination coeff. ;* - significance levelof 5% ; - - significance levelb-wap. regresji; a-wyraz wolny; r-wsp. korelacji; O-wsp. Determinacji; * - poziom istotnoaci 5%;** - poziom istotnoSci 1%

The values of regression coefficients "a" and "b" calculated using linearregression and correlation method vary from year to year according to themagnitude of infestation in those years. The values of regression coefficients"b" (that predicts how great the increase of V. jacobsoni females afterchemical treatment will be if the number of light females in the natural fallincreases by 1 individual) are lower as the apiary infestation becomes higher.It indicates the presence of factors that check the build up of mites in the yearswith higher infestation (Tab. 4; Fig.3). However, the greater the infestation ina given year the lower the value of coefficient "a" - a regression equationconstant.

In the second half of the season from Jl1 to S2 the calculated regressioncoefficient values "a" and "b" increased slightly but the tendency of theirincrease along with lower apiary infestation was not preserved (Table 4). Itwas due to atypical relationships in the years with higher infestation,especially in the year 1988. A substantial, as great as a 6-fold, increase in thenumber of light females in the natural fall in the period from Jl 1 to S2 ascompared to the increase in other years of the study points to an intensive mitepropagation. The regression coefficient "b" in that year was the lowestindicating that consequent upon the increase of the natural fall by 1 femalewas a smaller number of mites after chemical treatments. Indeed. the fall ofdark and light females after chemical treatments was the multiple by 7.0 in

190

----- ---_._. ------_ ....

that year and by 8.1 in 1990 of the respective falls of light females. Likewise,the values of correlation and determination coefficients in 1998 were lowerthan in the remaining years.

1988MIle feldar chemical conIroI· 735.n + 2.11·11811n1 mn. filiio.yp po zabIegech c:hemIc:znydl " 735. n + 2. 11· o.w MIInIny

'-0.1123800Iluao

1I =~I=III 12110

j 1 100il 400

oo 10 1. 110 2110 250 311 _ 400 •• 100 •• •• •• 7tIO____ 10_101·..-_ ••••••••••••"""'"

i-+- "•. _.--1-""

-'- 1,....00---- f..- •.. - -~--- -- :.--""" -- - -;-

.-tJ:. ..-- I-------- ....-- Cl

0

1992Mile ,... after c:hem1Ql control • 206.88 + 8,'7" •••••• mile ,..Osyp po abIegech clwnlc:znydl = 206,88 + 8,'7" o.w rwIurIIIny,.....

3101II32DO

I=I'::III 1200

;1 100u-o• • 100 1. 200 2SO MO 350 400 •• ••• 151 •• III 7tIO

____ In_ •••·~_.~"""'"

/,/

v: ,/

V ,-:f--

! / "'" v'-"V/ 1---'

-T/.~ ,i-

~/n 0.-:

"'~ i 1 ,~

1995Mite 1811after chemical c:on1rOI• 537,09 + 3,18· Mdu,.. mile ,..Osyp po zabIegach cIwnIc:znyd1 " 537,09 + 3,89" a.yp Mdu"'ny

r-'.71'

--- ,--'-

Fig. 3 Regression between the natural fall of Varroajacobsoni light - bodied femalesvs. the autumn infestation of the colonies.Zalemosc miedzy liczba samic Varroa jacobsoni ciemnych i jasnych Z osypupo zabiegach chemicznych a liczba samic jasnych Z osypu naturaInego dlacalego okresu obserwacji.

191

------ --- -- - --

1998MIte ,.. afW c:hemic:8I COIIIrOI• 11,79+ 17,01"nalInI miIII talOsyp po z8biegec:h c:t.nic:znydI • 11,79+ 17.01"oayp naIInIny

,.G,1t4-I'szoo

1=11=1& 1200

it -d400

o o 50 100 1110200 2SO 300 310 400 4110_ _ _ _ 7tO_oI_In_IoII·Uczba_w~ooypIo

! ! ' , ,I I I i i i j I1/

i ;'/ /. t-t--f-! I j :! 'I

!!/V1'1/ -- 1=: // / I I ! I i

~.' .1 !-1-1-

~il- ! i : I

./ ! i I ++- I ! i~ I I I i

Fig. 3 Regression between the natural fall of Varroa jacobsoni light - bodied femalesvs. the autwnn infestation of the colonies.Zaleznosc miedzy liczba samic Varroa jacobsoni ciemnych ijasnych z osypupo zabiegach chemicmych a liczba samic jasnych z osypu naturalnego dlacalego okresu obserwacji.

The relationships for the years with medium-high and low colonyinfestation followed a different pattern (1995, 1992, 1998). Regressioncoefficients "b" were much higher indicating that the increase in natural mitefall by 1 female caused higher increase in the number of mites towards the endof the season than that found in the high infestation years. The magnitude ofmite fall after chemical treatments in those years was the multiple ofrespective natural falls by 9.6, 13.06 and 20.8, The values of correlation anddetermination coefficients were also higher than in 1988 and 1990 whichindicates that in those years in 50% to 81% of cases the dependent variablewas assignable to the independent variable.

The autumn infestation of bee colonies based on the magnitude of naturalfall for the whole survey period was estimated using the regression equationcommon to the years of study in which counts were made in bottom insertsover the period from L 1 to W2.

The data listed in Table 5 show a good agreement between the meanestimated and actual values for the years 1988, 1992 and 1995. The estimatedmean autumn colony infestation by the mites was nearly the same as actualinfestation, the differences being from 3.4 to 38%. The low infestation year1998 was an exception - the estimated value (516 mites) was more than 3times higher than the actual figure (146 mites) which was 253%.

The counts of the natural mite fall during the whole season or its largepart would be difficult to do in commercial apiaries. Moreover, the cluesobtained as to the necessity of chemical treatments could be not timelyenough. Consequently, the regression analysis (common to all years of thestudy) was also extended to include the mobile mean of the natural fallobtained from counts of the natural fall of V.Jacobsoni females for the secondhalf of the season (from TIl to S2) made in three-week periods.

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-- --- --- --- -----

Table 5Estimated autumn infestation of colonies by Varroa jacobsoni females (C)based on the natural fall of light bodied females (A) as calculated from theregression equation common to the years of study in which survey was done

from July (11 I) to September (S2)Szacowane jesienne porazenie pasiek przez samice V.jacobsoni (ciemne i

jasne) (C) na podstawie naturalnego letniego osypu samic jasnych (A) wedlugr6wnania regresji wsp61nego dla lat badan, w kt6rych obserwacje prowadzono

w okresie od lipca (Ll) do wrzesnia (W2)

A B CDifference

Mean natural Actual ".eaii fall of females Estimated autumn infestation calculated by between

Year ~II (range) folloving autumn control regression equation - Szacowanajasienne Band C

Rok - Sredni osyp (range) - Rzeczywisty poraienie (samic ciemnych i jasnych) na ROinicanaturalny ~redni osyp samic podstawie letniego naturalnego osypu m~

samic jasnych ciemnych i jasnych po samic jasnych wedfug rOwnaniaregresji BiC(zakres) jasiennych zabiegach y = 490,22+3,69 x nat.fall (%)

chemicznych (zakres) r = 0,740; D = 550/.

1990 227 1847 1328 +28%*(43 - 648) (510 - 3350) (649 - 2888) (-27 -14)

1988 164 1150 1095 +5%(26 - 583) (260 - 2463) (550 - 2641) (-111 - 0.08)

1995 94 910 837 +8%(0 - 634) (146 - 2986) (490 - 2830) (-236 - 5,2)

1992 50 653 675 -3,4%**(1 - 224) (104 - 2288) (494 -1317) (-375 - 42)

1998 7 146 516 -253%(0 -47) (2 - 953) (498 - 664)

* - Signifies estimated autumn infestation higher than the actual mite fall after chemicaltreatments* ** + signifies estimated autumn infestation lower than the actual mite fall after chemicaltreatments* - - oznacza przewidywane jesienne porstenie rodzin wytaze od rzeczywistego osypupaso:tyt6w po zabiegach chemicznych- - + oznacza przewidywane jesienne porstemie rodzin nitsze od rzeczywiste go osypupaso:tyt6w po zabiegach chemicznych .

Once the correlation coefficients between the diurnal natural fall of lightfemales and the autumn infestation of colonies were compared it was foundthat until mid-June the majority of coefficients were low whereas later onsignificant and highly significant coefficients prevailed (Table 6).

Unfortunately. not too high correlation and determination coefficientssuggest that the summer diurnal natural fall cannot provide a basis forpredicting the autumn infestation of bee colonies. The strength of therelationship is lower (Table 6) than when natural fall from the whole surveyperiod or from Jll to S2 period is taken into account.

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Table 6

Values of correlation coefficients expressing the relationship between thenumber of light- and dark- bodied V.jacobsoni females following chemical

treatment and the number of light- bodied V.jacobsoni females in the naturalmite fall counts from the 3- week periods

Wartosci wsp61czynnik6w korelacji liniowej dla zaleznosci pomiedzy liczbasamic ciemnych i jasnych V. jacobsoni w osypie po zabiegach chemicznych a

liczba samic jasnych V. jacobsoni w osypie naturalnym wyliczonym z okres6w3- tygodniowych

Date Years of study· Lata bada"Okres 1988 1990 1992 1995 1998

M1,2,3 0,678** 0,125 0,486* 0,485**

M2,3,4 0,685** -0,229 0,320 0,276

M3,4Jn1 0,698** -0,136 0,288 0,245

M4Jn1,2 0,691 ** -0,097 0,298 0,432**

Jn1,2,3 0,844** 0,478** 0,395* 0,353

In 2,3 0,914** 0,265 0,570** 0,404*

In 3,4J11 0,872** 0,485** 0,614** 0,110

Jn4JI1,2 0,777** 0,645** 0,511 ** 0,246

JI1,2,3 0,778** 0,186 0,749** 0,460* 0,348

JI2,3,4 0,751 ** 0,096 0,776** 0,384 0,587**

JI3,4,5 0,658** 0,144 0,743* 0,590** 0,572**

J14,5A1 0,556** 0,344 0,801 ** 0,631 ** 0,592**

J15A1,2 0,525* 0,381 0,838** 0,643** 0,160

A1,2,3 0,619** 0,439* 0,727** 0,652** 0,695**

A2,3,4 0,597** 0,523** 0,641 ** 0,640** 0,882**

A3,4S1 0,609** 0,574** 0,653** 0,665** 0,923**

MS1,2 0,581 ** 0,562** 0,630** 0,715** 0,932**

\

M· May; Jn- June; JI • Juli A· August; S·September; 1, 2, 3, 4, 5 • succeeding weeks* • significante level of 5% ; - • significante level*. poziom istotnosci 5%; -. poziom istotnosci 1%

Based on the summer diurnal natural fall of light females calculated fromthe three-week count periods and on the regression equations a predictionchart was drawn up. The chart lists predicted autumn infestations of beecolonies (number of mites) against mean diurnal natural falls over differentcount periods of 1,3,3 12 light V.jacobsoni females (Tab.7).

194

-----------~-- -~~~~--

Table 7Estimated autumn infestation of bee colonies by V.jacobsoni based on summer

diurnal natural mite fall counts from 3 - week periods and calculation fromregession equations common to all study years as shovn in foregoing table

Szacowane jesienne porazenie rodzin pszczelich przez V.jacobsoni napodstawie dobowego letniego osypu naturalnego pasozyta wyliczonego z

okres6w trzytygodniowych, obliczone wedlug wsp6lnych dla wszystkich latbadati r6wnati regresji

Estimated number of V. jacobsonl females present in colonies with diurnal natural fall otSiudy period Przewidywanaliczbasamic Varroa jacobsoni ciemnych i jasnych obecnych w rodzinach:Okres bada"

1 2 3 4 5 6 7 8 9 10

In 4 Jll,2 1989 3560 5132 6704 8275 9523 11035 12990 14562 16133

Jl1,2,3 1480 2488 3496 4505 5513 6521 7529 8537 9546 10553

Ji 2,3,4 1309 2130 2951 3773 4594 5415 6236 7057 7879 8700

JI3,4,5 929 1356 1782 2208 2635 3061 3487 3914 4340 4766

JI4,5 Al 929 1043 1311 1579 1847 2115 2383 2651 2919 3187

JI5A 1,2 725 963 1200 1438 1675 1913 2150 2387 2625 2863

A 1,2,3 667 899 1130 1361 1592 1823 2054 2285 2516 2747

A2,3,4 614 756 898 1040 1183 1325 1467 1609 1751 1893

A3,4 Sl 572 700 830 959 1088 1217 1346 1475 1604 1733

A4 Sl,2 566 705 844 983 1121 1260 1399 1538 1676 1815

In- June; JI - Juli A- August; S-5eptember; 1, 2, 3, 4, 5 - succeeding weeksIn-czerwiec; JI-lipiec; A-sierpien; 5-wrzeaien; 1,2,3,4,5- kolejne tygodnie mieail¥=8

The predicted figures of autumn colony infestation thus calculated areburdened with error. As was found earlier each year of study is characterisedby a different, peculiar rate of mite build up. That is why regression equationscalculated separately for each year and even for each count period differ fromone another. The calculated differences between the autumn colony infestationthus estimated (expressed as the average predicted number of mites incolonies) and the actual mite fall after chemical treatments were characterizedby substantial variation from - 362 to + 826 mites (Table 8). In the majority ofcases the estimated autumn infestation was lower than the actual infestation. Itindicates that the diurnal fall of light-bodied females calculated from shorterperiods cannot be treated in its own right as a reliable parameter to estimatethe autumn infestation of bee colonies by the mite.

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-- ---------- --~---~---- ~- -

Table 8

Difference between the estimated autumn infestation of colonies by light anddark- bodied V.jacobsoni females and the actual mite fall following chemical

treatment over the periods and years of studyRoznica miedzy szacowanym (na podstawie sredniego dobowego osypu

naturalnego samic jasnych) jesiennym porazeniem pasiek przez samice V.jacobsoni ciemne i jasne a rzeczywistym osypem po zabiegach chemicznych w

poszczegolnych terminach i latach badan

Study period Year of study - Rok bad;mOkreS bad;m 1990 1988 1995 1992 1998

Jn4 J11,2 +431 +37 -110 -302

JI1,2,3 +359 +396 +25 -51 -356

JI2,3,4 +482 +449 +36 -98 -358

JI3,4,5 +826 +434 +82 -80 -361

JI4,5 A1 +838 +437 +81 -44 -362

JI5 A1,2 +611 +374 +104 -30 -343

A 1,2,3 +384 +203 +120 +34 -292

A 2,3,4 +546 +112 +230 +70 ·340

A3,451 +590 +86 +175 +118 -326

A451,2 +578 +47 +215 +109 -314

* • signifies estimated autumn infestation higher than the actual mite fall after chemicaltreatments** + signifies estimated autumn infestation lower than the actual mite fall after chemicaltreatments* - - oznacza przewidywane jesienne poraienie rodzin wyisD od rzeczywistego osypupasotyt6w po zabiegach chemicznych** - + oznacza przewidywane jesienne poraiemie rodzin "lisH od rzeczywiste go osypupasotyt6w po zabiegach chemicznych .

CONCLUSIONSI. The mean number of dead light-bodied females which fell to the wire net

bottom inserts stayed at a similar level in May and in June over all yearsof the study. In July and in August the number of light females rose two-to sixfold compared to previous month's figures

2. Likewise, there was an increase in the number of V.jacobsoni females inthe diurnal natural fall calculated from counts made in three-weekperiods.

3. The analysis of the natural fall of light females allows to arrange theyears in the same order (1990, 1988, 1995, 1992 and 1998) as they werearranged according to the magnitude of infestation

4. The majority of correlation coefficients between the diurnal natural fallof light females and the autumn infestation of colonies until mid-June

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were low and insignificant whereas later on significant and highlysignificant coefficients prevailed

5. Each year of study is characterised by a different, peculiar rate of mitebuild up

6. The calculated differences between the autumn colony infestation thusestimated (expressed as the average predicted number of mites in colonies)and the actual mite fall after chemical treatments were characterized bysubstantial variation from - 362 to + 826 mites

7. Diurnal natural fall of light-bodied females calculated from shorter periodsof counts cannot be treated as a reliable parameter to estimate the autumninfestation ofbee colonies by the mite.

REFERENCESLe Conte Y., Arnold G. (1987)- Influence de rage des abeilles (Apis

mellifica L.)et de la chaleur sur le comportement de Varroa jacobsoni Oud.Apidologie 18(4): 305-320

Lie big G. (1 994) - Entsehung und Zusammenfasung des natiirlichenMilben(ab)falls. Dt. Bienen J. 2(3): 141-143

Liebig G., Schlupf U., Fremuth W., Ludwig W. (1984)-Ergebnisse der Untersuchungen uber die Befallsentwicklung der Varroa -Milbe in Stuttgart - Hohenheim in 1983. ADIZ. 18(8): 185-191

Loob N., Martin S. (1997)- Mortality of Varroa jacobsoni Oudemansduring or soon after the emergence of worker and drone honeybees Apismellifera L.Apidologie 28(6): 367- 374

M art inS. J ., K e m pD. (1 99 7 ) - Average of reproductive cycles performedby Varroa jacobsoni in honey bee (Apis mellifera) colonies. J.apic. Res.36(3/4): 113-123

R a d e m a c her E. (1 9 8 5 ) - 1st eine Befallsprognose aus dem natiirlichenTotenfall von Varroa jacobsoni moglich? Apidologie 16(4): 395-406

S t e i n e r J. (1 9 9 3 ) - Verteilung von Varroa jacobsoni im DrohnenfreienBienevolk. Apidologie 24(1): 45-50

SAMICE JASNE JAKO PARAMETR PRZYDATNY W OCENIEPORAZENIA RODZIN PSZCZELICH PRZEZ PASOZYT A

VARROA JACOBSONIBieiikowska M., Kn n e p a c k a Z.

S t res z c zen i e

W osypie naturalnym obok samic ciemnych, ktore gina smiercia naturalna i opadaja nadno ula, samc6w i stadi6w rozwojowych pasOZyta usuwanyeh przez P!lZczoIy podczasczyszczenia komorek, znajduja, siCCrowniez samice jasne, nie wybarwione wychodzace z

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kom6rek wraz z wygryzajacymi si~ doroslymi owadami, ale niezdolne do zycia, Poziomosypywania sictpasoZyt6w i udzial w Dim samic ciemnych i jasnych zwiazany jest §Ci§lezwygryzaniem sictjak rowniez rodzajem wygryzajllCego sictczerwiu.

Udzial samic jasnych w osypie naturalnym bywa r6my i mote wynosie 49%, 70%, a wbadaniach Rademacher nawet 97%. W badaniach prowadzonych w OddzialePszczelnictwa w latach 1988, 1990, 1992, 1995 i 1998r. procentowy udzial samic jasnychw osypie naturalnym wynosil srednio 32,5% (od 25% do 40,5%). Liczba tych samic wmaju i w czerwcu utrzymywala sictna niskim niemaljednakowym poziomie (srednio okolo7 samic/rodzine/miesiac/rok), gwaltowoie wzrastala w lipcu (srednio okolo 21samic/rodzine/miesiac/rok) i w sierpniu (srednio okolo 60 samiclrodzinct/miesillCirok), awe wrzesniu spadala bardzo wyrainie eo mialo niewatpliwie zwiazek ze mmiejszaniem sictilosci czerwiu w rodzinach.

Poszczegolne lata badan romily sictmiedzy soba wielkoscia osypu naturalnego samicjasnych, ale wielkosc tego osypu - szczegolnie w drugim okresie sezonu od poczatku lipcado polowy wrzesnia - pozwalala na uszeregowanie lat w tej samej kolejnosci jakuszeregowanie lat wedhig nasilenia inwazji wyrazonego liczba samic ciemnych i jasnychrazem po chemicmych zabiegach leczniczych, Stwierdzono rowniez wystepowaniewysoko istotnych korelacji miedzy liczba samic jasnych w osypie naturalnym z calegookresu obserwacji i okresu od lipca do polowy wrzesnia, a liczba samic ciemnych i jasnychw osypie po chemicznych zabiegach leczniczych ( w 1988 r = 0,652··; w 1990 r =0,768"; w 1992 r = 0,893"; w 1995 r = 0,718" i w 1998 r = 0,889"). PoslugujllC sictrownaniem regresji wsp6lnym dla wszystkich lat badail oszacowano jesienne porazenierodzin pszczelich na podstawie wielkosci osypu naturalnego samic jasnych z calego okresuobserwacji. Stwierdzono duza zgodnosc miedzy srednimi wielkosciami szacowanymi arzeczywistymi w latach 1988, 1992 i 1995. Wyjlltek stanowil rok 19980 skrajnie niskimporazeniu, w ktorym wartosc szacowana byla ponad 3-krotnie wyzsza niZ rzeczywista.

Obserwacje osypu naturalnego w ciagu calego sezonu bylyby trudne do zrealizowaniaw pasiekach produkcyjnych, dlatego analize regresji wspolna dla wszystkich lat badanprzeprowadzono dla dobowego osypu naturalnego wyliczonego z kr6tszych okres6wobserwacji. Na tej podstawie opracowano tabele prognostyczna, kt6ra podajeprzewidywane jesienne porazenie rodzin pszczelich, gdy dobowy osyp wyliczony ztrzytygodniowych okresow obserwacji wynosi I, 2, 3, .i 10 samic jasnych Varroajacobsoni.

Obliczone roznice miedzy tak szacowanym jesiennym porazeniem rodzin pszczelich arzeczywistym osypem pasozytow po zabiegach chemicmych charakteryzowaly bardzoduze wahania od -362 do +826 pasozytow. Swiadczy to 0 tym, ze dobowy osyp samicjasnych wyliczony z krotkich okresow obserwacji nie mote bye traktowany jakooddzielny, pojedynczy i wiarygodny parametr w szacowaniu porazenia rodzin pszczelichprzez pasozyta.

Slowa kluczowe: Varroajacobsoni, porazenie, samicejasne.

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